In my Kubuntu 12.04, every time I tried to save a libre office document for the first time or did a save-as (basically it seemed to be whenever the file dialogue would pop up. The program would eat it without saving a damn thing after I either pressed “Save” or “Cancel.” It did not however do so when I would save to an already created document (no file dialogue there).
Skip down to update to see an even better way.
Anyway, I didn’t exactly fix it but I did find a work-around. I uninstalled the package “libreoffice-kde” and everything was all better. Sure, the program doesn’t look quite as pretty but all the functionality is there, it’s stable and it works well. Don’t know why it works but it did. If it doesn’t cure your problems, it’s easy enough to reinstall with no hassle.
Update: Some folks below brought it to my attention that there’s a more sophisticated (less neanderslobish) way to fix the issue. Go to Tools -> Options -> LibreOffice -> General. Then, look for the box next to “Use LibreOffice dialogues;” it’s most likely unchecked. By checking it, I was able to keep libreoffice-kde and have the program work like a charm. This was much better than running the software without the kde embelleshemnts…it just looked so…grey. Thanks so much Alefa and “m.”
Neanderslob VS Technology 
Hi, just wanted to mention that there’s a less radical solution: Keep the libreoffice-kde package installed, but use LibreOffice’s own open/save dialogue instead of the KDE one (under Options –> General). At least that works for me.
Wow, thanks; your tip worked like a charm. Another fellow followed up a couple days later with similar advice. I wasn’t really crazy about having all the KDE modifications off; this is a much better solution. I’ll add it to my post!
Same problem here.
I checked Tools/Options/LibreOffice/General/OpenSaveDialogs “Use LibreOffice dialogs” and it worked.
Wow, thanks; your tip worked like a charm. I wasn’t really crazy about having all the KDE modifications off; this is a much better alternative. I’ll add it to my post!